An electronic module, such as may be arranged at a desired location in a manufacturing process, has an internal address which is used to communicate with the module. A module, for example, may be monitored to obtain information about the module or about the environment adjacent the module. Some information might indicate, for example, the presence or absence of an article at a particular location, such as on a conveyor belt assembly.
Typically, several electronic modules are utilized. Each module has an internal address which may be set during installation of the module. In conventional systems, the internal address of each module often is set manually, such as by manipulating one or more dip-switches. As a greater number of electronic modules are used or as a module is replaced or as new modules are added, the likelihood of address-related errors increases. Accordingly, it is desirable to provide an apparatus and method in which the internal address of each module may conveniently be set during an automatic addressing process.
U.S. Pat. No. 5,204,669 to Dorfe et al. discloses a method and apparatus for dynamically assigning addresses to a plurality of fully powered programmable function modules. This patent requires that a programmable controller initiate the addressing process by transmitting an enabling signal to a first function module over a control line. The programmable controller then transmits an address to the first module.
The process continues by the first function module obtaining and storing the address from the controller. The first function module internally modifies the address and then transmits an enable signal via a control line to another module. The enable signal notifies the next module that it may receive the modified address information. The first function module then transmits the modified address to the next module over the serial communications bus.
This process continues until the last module receives its address from an adjacent preceding module. The last module has a termination circuit which sends a return signal back to the controller over a second control line after the last module receives modified address information from a preceding module. In response to the return signal, the controller may determine information about the other modules.
The addressing scheme of the Dorfe et al. Patent requires a specially configured programmable controller to initiate the addressing process. Each function module also is fully powered and configured to modify and transmit addresses to downstream modules. In addition, a second control line is required to electrically connect the last module to the programmable controller for sending the return signal back to the controller.
U.S. Pat. Nos. 5,262,771 and 5,495,575 both to Hermann et al. disclose similar methods of self-addressing individual processor units connected in a network configuration. Similar to the Dorfe et al. patent, the individual processor units in each of these patents receive address information from a preceding adjacent processor unit. The processor unit then modifies the address information for subsequent transmission to the next connected processor unit or units. These systems, however, are more complex than that disclosed in the Dorfe et al. Patent. Specifically, the systems described in the Herrmann et al. patents have additional components for accommodating multiple branches of different processor units.